Research on a 4G (4th Generation) mobile communication system, a next-generation communication system, is actively ongoing to provide services with various QoS (Quality of Service) with a transfer rate of about 10 Mbps to users. The 4G mobile communication system is being standardized to aim at cooperatively operating a wired communication network and a wireless communication network and providing integrated services, beyond simple wireless communication services such as mobile communication systems of a previous generation.
As a large capacity communication system, which may process and transmit various information such as images, radio data, or the like, beyond voice-centered services, is requested, development of a technique allowing transmission of large capacity data similar to the capacity of the wired communication network to the wireless communication network is on demand.
Thus, a proper channel coding method that can improve a system performance by minimizing a loss of information and increasing the efficiency of system transmission is recognized and admitted as an essential factor. In general, in order to reduce information loss, the reliability of a system is increased by using various channel codings depending on the properties of channels, one of which is a repetition coding. In the repetition coding, original data to be transmitted is repeated to generate a plurality of same data as the original data. Because the duplicate data, which is the same as the original data, are generated and transmitted together with the original data, the probability of a transmission error can be reduced.
In general, in an OFDM (Orthogonal Frequency Division Multiplexing) system, spectrums of sub-channels overlap with each other while maintaining cross-orthogonality, having good spectrum efficiency, and because OFDM modulation/demodulation is implemented by IFFT (Inverse Fast Fourier Transform) and FFT (Fast Fourier Transform), a modulating/demodulating unit can be effectively implemented digitally and resistant to a frequency selective fading or a narrowband interference.
Despite such advantages, the OFDM system is disadvantageous in that it has a high peak-to-average power ratio (PAPR). The OFDM transmits data by using many carriers, so a final OFDM signal has the size of amplitude tantamount to the sum of amplitude sizes of the respective carriers, having a severe change width of amplitude, and if the phases of the carriers correspond, a quite large value can be obtained. In particular, in case of using the repetition coding in the OFDM system, the same data is repeatedly transmitted, and for uplink, a resource allocation region does not have a square shape, making it difficult to lower the PAPR and possibly degrading the performance of the system.
Thus, in order to data by using repetition coding, a method for lowering the PAPR is required.